Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!samsung!uunet!dg!vis01!mpogue
From: mpogue@vis01.dg.com (Mike Pogue)
Newsgroups: comp.graphics
Subject: More on the Patent question....
Keywords: Cadtrak patent XOR split-screen
Message-ID: <646@dg.dg.com>
Date: 17 Jul 90 14:55:16 GMT
Sender: root@dg.dg.com
Reply-To: mpogue@dg.dg.com
Organization: Data General, Westboro, MA.
Lines: 63


  To continue a thread from comp.arch, concerning 
patentability of certain common graphics operations:

  In comp.arch, there was much discussion about the current
Cadtrak activity.  Cadtrak is the alleged inventor of several
graphics concepts, including XOR of a frame buffer.

  I talked to our law department, and they gave me a laundry list
of information that they (and every other company currently 
paying royalties) would be interested in.

  Here's the summary:

  Cadtrak claims that they invented several things in the area
of computer graphics.  Their patent, reissued as #31,200, was originally
filed on January 19, 1976.  Based on US patent law, if anybody can
show "prior art", i.e. a published (or otherwise substantiated)
reference, with a publication date of earlier than January 19, 1975,
then Cadtrak would NOT be considered to have been the inventor.

  Here's what Cadtrak is claiming they invented:

1) XOR of the frame buffer.  Any hardware that accesses a frame
buffer, using exclusive OR to draw something (line, etc.).  Drawing
the same thing again, also in XOR mode, erases the thing from the screen.

   They claim that although this is obvious now, that it wasn't back
then, and nobody previously had done exclusive OR on frame buffers.

2) Hardware PAN.  Any hardware that allows you to change a pointer,
and give the effect of panning across an image larger than the
actual physical screen.

3) Hardware split screen.  Any hardware that allows you to specify
two such pointers, such that you can look at two virtual frame buffers
on one screen.  Of course, this applies to more than two, and it applies
to horizontal split, vertical split, and windowing.

4) Double buffering.  Any hardware that provides for two virtual buffers,
with one being viewed at any one time.  Again, this is very similar to
the Hardware PAN and Split Screen claims, in that there are pointers that
can be used to quickly change what shows up on the screen.

5) Hardware ZOOM, using pixel replication.  Any hardware that permits
zooming in on an image, by replicating the pixels in a square pattern
to make them appear bigger.

  Anybody who can provide a reference to an article, paper, film, or
lab notebook referring to these concepts, and dated before Jan 19, 1975,
will become famous (well, OK, almost famous), by stepping forward.  My
guess is that there are many millions of dollars in royalties involved
here, not to mention the basic freedoms in question here.

  E-mail direct to me is chancy, at best, so best to post the reference,
if possible.  The future of graphics is in the balance! (Well, it sounds
good, at least....)


Mike Pogue
Data General Corp.

Speaking for myself alone, not my company.